The invention relates to a device for wet granulation of liquid slag.
In wet granulation a liquid slag flow is introduced into a powerful water flow, the liquid slag entrained by the water flow being granulated, solidified and cooled. The granulate is subsequently dewatered.
Devices for wet granulation of liquid slag are known, for example, from the blast furnace sector. They comprise a granulating basin with an injection device for the granulating water as well as equipment for dewatering the granulate. Conventional dewatering equipment comprises a decanting basin separate from the granulating basin, in which the slag granulate settles.
In wet granulation there is a non-negligible explosion hazard due to both the release of hydrogen and the explosive overheating of water vapour. In order to reduce this explosion hazard it is necessary to operate with very large water flows. These large water flows necessitate, of course, large space-consuming decanting basins.
To avoid such space-consuming decanting basins, it is known to use dewatering drums as described, for example, in U.S. Pat. No. 4,204,855. In large blast furnace plants such dewatering drums quickly pay off due to their high dewatering capacity. For smaller slag quantities, as for example produced in electric steel plants, wet granulation with a dewatering drum downstream is however too expensive.
The object of the present invention is to provide a simple and at the same time very compact device for wet granulation of liquid slag.
A device for wet granulation of liquid slag according to the invention comprises a granulating basin with an injection device for the granulating water, a decanting basin, separate from the granulating basin, in which the slag settles as granulate, as well as a device for introducing the granulate/water mixture from the granulating basin into the decanting basin. This device comprises at least one oblong distributor duct, which extends over the decanting basin and which has outlets for the granulate/water mixture distributed over the length of its underside. These outlets may, for example, comprise an outlet slot or several outlet openings arranged one behind the other. In the decanting basin a vertical, open at the bottom inflow shaft, into which the outlets for the granulate/water mixture discharge, is arranged under the at least one distributor duct. This inflow shaft can for example easily be formed by two screening walls attached to the distributor duct. The granulate/water mixture can be introduced into the decanting basin largely without turbulence through the distributor duct, its outlets and the inflow shaft. This ensures that the slag granulate also settles satisfactorily in relatively small decanting basins. The present invention consequently enables the creation of a compact device for wet granulation of liquid slag with extremely simple means.
The decanting basin advantageously comprises overflow devices for the granulating water at its upper edge. The xe2x80x9cclarifiedxe2x80x9d granulating water is removed from the decanting basin via these overflow devices during the granulation and, if necessary, returned to the injection device in the granulating basin. In a preferred embodiment the distributor duct is positioned lower than these overflow devices and is consequently below the water level in the decanting basin.
For withdrawal of the granulate from the decanting basin the latter advantageously comprises at least one funnel-shaped recess with an outlet connection piece and a shut-off valve for closing the outlet connection piece.
Utilization of space in the decanting basin is optimized by the fact that the inflow shaft and the at least one funnel-shaped recess have a common plane of symmetry. A particularly compact device can be achieved by a decanting basin having several funnel-shaped recesses one behind the other, the inflow shaft and the funnel-shaped recesses one behind the other having a common plane of symmetry.
The granulating basin is advantageously designed as an oblong basin with a bottom surface, two lateral faces and two end faces. The injection device for the granulating water is arranged at a first end face of this basin and the at least one distributor duct forms its discharge opening into the granulating basin at the opposite end of the basin.
In a preferred embodiment the injection device for the granulating water comprises a chamber, which surrounds the first end of the basin and has outlet nozzles for the granulating water. These outlet nozzles for the granulating water are preferably arranged in the two lateral faces as well as in the first end face of the basin.